Final answer:
Acetaminophen in high doses should not be used for chronic pain due to its toxic metabolite leading to potential severe liver damage.
Step-by-step explanation:
The medication that should NOT be used to treat chronic pain due to a toxic metabolite is acetaminophen when taken in high doses. While commonly used medications such as oxycodone, hydrocodone, morphine, and others are prescribed to relieve moderate to severe pain, they must be used with caution due to risks of addiction, abuse, and overdose.
However, specifically, acetaminophen can lead to severe liver damage if overdosed, hence it has a toxic metabolite that can be particularly harmful if used improperly for chronic pain management.